This invention relates to a method of fitting a coil onto a bobbin, as well as to a circuit breaker coil and bobbin assembly.
Circuit breakers generally make use of an overload coil which is wound onto a bobbin carried on a magnetic frame within the circuit breaker housing. In the assembly procedure, a unitary double-flanged bobbin is typically loaded onto a coil winding machine, and the overload coil is wound onto the bobbin. The necessary coil terminations are completed after the coil and bobbin assembly has been removed from the coil winding machine. A sensing tube is then passed through the coil and bobbin assembly, which is in turn mounted on a magnetic frame.
The loading of the bobbin onto the coil winding machine and the subsequent winding of the coil is a process which does not lend itself to automation, and significant setting-up time is required. In addition, each bobbin has to be manufactured to relatively precise tolerances in order to ensure that it fits onto the coil winding machine. Any additional assembly steps which need to be performed on the overload coil, such as the application of flexible conductors and the like, have to be performed with the bobbin already in position.